The venue of the seminar: The University of Queensland, Room 78-622, St Lucia Campus, Brisbane

Title: Continuous Queries and Reactive Behavior Management in Moving Object
Databases
Speaker: Prof. Peter Scheuermann (Northwestern University, USA)

Abstract:
Unlike traditional applications where queries are instantaneous, many queries of interest in moving object databases (MOD) are continuous in nature and require constant re-evaluation over the history of the objects. We assume that that the motion of objects is represented by trajectories, which consists of a sequence of 3D points. We present first a comprehensive set of techniques, both static and dynamic, for minimizing the costs involved in reevaluating continuous queries in response to bulk updates. The static techniques correspond to specifying the values of various semantic dimensions of trigger execution. The dynamic techniques include an in-memory shared reevaluation algorithm, adapting  query indexing techniques to trajectory data, and utilizing ordering based on space-filling curves to improve the I/O efficiency. We next address the problem of handling event notification in MOD, by introducing a class of dynamic topological predicates, such moving along and moving towards. We show that traditional triggers are inadequate for handling the reactive behavior of these topological predicates since they repeatedly evaluate the conditions on the entire past trajectory. Motivated by this we introduce a new paradigm for expressing reactive behavior in distributed environments in which data continuously changes over time and which allows users to explicitly specify how the triggers should be (self) modified. We call this paradigm Evolving and Context-Aware Event Condition Action (ECA) 2. Our model combines reactive behavior with proactive impact by modifying dynamically the event/conditions and actions monitored. Since both the monitored event and the condition part of the trigger can be continuous in nature, we introduce the concept of metatriggers to coordinate the detection of events and the evaluation of conditions.

Biography:
Professor Peter Scheuermann is a Professor of Electrical Engineering and Computer Science at Northwestern University. He has held visiting professor positions with the Free University of Amsterdam, the University of Hamburg, the Technical University of Berlin and the Swiss Federal Institute of Technology, Zurich. During 1997-1998 he served as Program Director for Operating Systems at the NSF.  Dr. Scheuermann has served on the editorial board of the Communications of ACM, The VLDB Journal, IEEE Transactions on Knowledge and Data Engineering and is currently an associate editor of Data and Knowledge Engineering and the International Journal of Next-Generation Computing.  Among his professional activities, he has served as General  chair of the ACM-SIGMOD Conference in 1988,  General chair of the  ER'2003 Conference and  more recently as Program Co-Chair of the ACM-SIGPATIAL conference in  2009.  He was a member of the ACM-SIGMOD advisory board, and prior to this he chaired the ACM-SIGMOD awards committee His  research interests are in  distributed database systems, mobile computing, sensor networks and data mining. He has published more than 120 journal and conference papers. His research has been funded by NSF, NASA, HP, Northrop Grumman, and BEA, among others. Peter Scheuermann is a Fellow of IEEE and AAAS (American Association for the Advancement of Science).